In the packaging of liquid goods, e.g. milk, cream, juice or the like in packing containers of the non-returnable type, automatic packing machines are used which by means of a pipeline are connected to units for the treatment and transport of the contents to the machine. To ensure that the contents flow to the packing machine at an even and predetermined volume per unit of time, a so-called constant-flow valve is usually present upstream of each packing machine which sees to it that irrespectively of pressure variations in the feed line the flow is kept constant. The hygienic demands on such a valve are very high, especially when the packing machine is of the aseptic type, that is to say when it manufactures packages which are to be filled with contents previously subjected to sterile treatment.
In other words the use of constant flow valves in product lines implies that the valve must be of such a design that it can be cleaned and washed in a simple manner. When the valve is intended for sterile contents it is also important that it should be of a shape allowing it to be sterilized after the washing. Such a sterilization may be done, e.g., with the help of steam or some chemical sterilizing agent, e.g. hydrogen peroxide.
Constant flow valves known previously are of a design which makes them little suitable for use in conjunction with aseptic packing machines. The valves comprise a valve housing with a movable valve body whose position is controlled by an operating mechanism as a function of the actual pressure in the line to which the valve is connected. The operating mechanism and its components are usually of an unprotected design and will therefore come into contact with the contents thus making it difficult to clean the valve and causing it to be wholly unsuitable for use with sterile contents.